Method and apparatus for fumigation

ABSTRACT

A fumigating method for fumigating a large place such as a cultural facility with a compact installation and an apparatus used for the fumigating method. The fumigating method which comprises providing an argon gas tank ( 1 ) and a PO tank ( 8 ) filled with liquid propylene oxide, introducing an argon gas fed from the argon gas tank ( 1 ) and liquid propylene oxide fed from the PO tank ( 8 ) in advance to a gas-liquid mixer ( 5 ) for mixture, introducing the resultant gas-liquid mixture from the gas-liquid mixer ( 5 ) to a vaporizer ( 25 ) for vaporization, and then introducing the resultant gas mixture to a place ( 31 ) to be fumigated; and an apparatus for conducting such a method.

TECHNICAL FIELD

The present invention relates to a fumigating method for preservingvarious cultural assets and to an apparatus used therefor.

BACKGROUND ARTS

Heretofore, to protect a variety of valuable cultural assets (historicalarchitecture such as temples and shrines, culturally highly-valuedcalligraphic works and paintings, books and craftworks), exhibitionhalls in cultural facilities such as museum, reference library andlibrary, and other materials, places and the like, which requiresterilization-or insect killing, from harmful biological organisms suchas harmful insects, molds and bacteria and to preserve them at goodconditions, it has been generally conducted that such objects areenclosed air-tightly and a fumigation gas obtained by a fumigant, highlyeffective to sterilize harmful biological organisms, is filled in such aspace for fumigation. This fumigating method has the advantage thatharmful organisms can be eradicated at once without deterioratingqualities of cultural assets and the like.

As a fumigating agent for use in cultural assets and the like, a liquidmixture of ethylene oxide (pesticide) and methyl bromide (a diluent) hasbeen mainly used. However, ethylene oxide is designated as a specificchemical substance due to its carcinogenicity so that its conditions foruse are strictly restricted, while methyl bromide is designated as asubstance that depletes the ozone layer in accordance with MontrealProtocol so that its use is also restricted. For this reason, theaforesaid fumigating agent is substantially impossible for use in thefield of preservation of cultural assets.

As an alternative for the aforesaid fumigating agent, a gas mixtureobtained by gas-liquid mixing propylene oxide (pesticide) and argon (adiluent) has been developed for use as a fumigating gas and has beenproposed (see Japanese Unexamined Patent Publication No. JP2000-281506).Since propylene oxide (hereinafter just referred as “PO”) has explosivelimits of 2.8 to 37% by volume in the air, a safe dispensing method isrequired so as to be outside a combustible range (or a range ofinflammability), when PO evaporates, or in a place (space) to befumigated including an inlet tube for introducing PO thereinto.Therefore, was developed a dispensing method for maintaining POconcentration of not more than 2% by volume by adding argon forcontrolling the PO concentration so as to be outside the combustiblerange, and such a gas mixture has been used as a fumigating gas.

This method comprises blowing depressurized argon gas at a specific rateinto a tank filled with-liquid PO and warming the tank from outside bymeans of warm water of about 40° C. for imparting latent heat requiredfor evaporation (477 J/kg) so as to control PO concentration. Thismethod is just referred to “a bubbling method” hereinafter. The POconcentration of the gas mixture caused in the bubbling method is about20% by volume, and further argon gas is added thereto so as to dilutethe resultant mixture within a range of 0.5 to 2.5% by volume. For thisreason, after a place to be fumigated is made into an argon gasatmosphere, the gas mixture caused in the bubbling method is introducedinto the place from the tank and is mixed with argon gas for dilution inthe place for homogenization.

An example of a fumigating apparatus for using such technology isillustrated in FIG. 5. In FIG. 5, a reference numeral 51 denotes anargon gas tank filled with compressed argon gas. A reference numeral 52denotes a decompression valve aligned on an argon-gas takeout tube 53and reduces the pressure (14.7 MPa) of the argon gas taken out of theargon gas tank 51 to a specific pressure (0.3 MPa). A reference numeral54 is a purge argon gas inlet tube for introducing the argon gas takenout of the argon-gas takeout tube 53 into a place 57 to be fumigated,and the purge argon gas inlet tube is provided with an on/off valve 55and an argon gas flowmeter 56.

A reference numeral 58 denotes a PO tank, made of stainless steel, inwhich liquid PO is encapsulated, and comprises a lower liquid phaseportion 58 a comprising liquid PO and an upper gas phase portion 58 b. Areference numeral 59 is an inlet tube for introducing argon gas takenout of the argon gas takeout tube 53 as bubbling gas into the PO tank58, and is provided with an on/off valve 60 and an argon gas flowmeter61. The bubbling argon gas inlet tube 59 extends to the bottom insidethe PO tank 58.

A reference numeral 62 denotes a warm water bath for storing warm water62 a into which the PO tank 58 is put. A reference numeral 63 is aheater for heating warm water 62 a so that the temperature of the warmwater 62 a is within a range of 30 to 35° C. A reference numeral 64 is agas mixture inlet tube for introducing gas mixture within the upper gasphase portion 58 b of the PO tank 58 into a place 57 to be fumigated andextends from the upper portion of the PO tank 58 to the place 57. Areference numeral 65 is an apparatus for mixing the gas mixtureintroduced into the place 57.

A fumigating process is conducted, for example, by means of theaforesaid fumigating apparatus as follows. First, an on/off valve 55 isopened and an on/off valve 60 is closed, argon gas of the argon gas tank51 is introduced via the argon gas takeout tube 53 and purge argon gasinlet tube 54 into the place 57 to be fumigated. As a result, theatmosphere of the place 57 is replaced with argon gas. Then, the on/offvalve 55 is closed and the on/off valve 60 is opened, argon gas of theargon gas tank 51 is withdrawn through the argon gas takeout tube 53 andthe bubbling argon gas inlet tube 59 into the lower liquid phase portion58 a of the PO tank 58, wherein the liquid PO is vaporized by thebubbling effect of the argon gas and the PO gas is stored in the uppergas phase portion 58 b together with the argon gas.

The gas mixture of PO gas and an argon gas accumulated in the upper gasphase portion 58 b of the PO tank 58, in which the PO gas concentrationis kept constant, is supplied from the upper gas phase portion 58 b ofthe PO tank 58 to the place 57 via the gas mixture inlet tube 64. Atthat time, the amount of the gas mixture and the like are adjusted suchthat the PO gas concentration in the place 57 is not more than 2% byvolume. Thus, harmful organisms in the place 57 are eradicated byfumigating the place 57 for a specific period and then the fumigatingprocess is completed.

However, since the PO tank 58 per se is immersed into warm water 62 a ofthe warm water bath 62 in the aforesaid bubbling method, theinstallation is enlarged. Further, to pass the latent heat required forevaporation from a surface of the PO tank 58, the maximum amount ofdispensing the fumigating gas per minute is limited to 0.1 kg/unit,because heat transfer area of the PO tank 58 is small. Since the amountof a fumigating agent for use in cultural facilities or the like is 50g/1 m³ of dimensions and total PO amount is 100 kg to 1500 kg, manyfumigating apparatus are required.

In view of the foregoing, it is an object of the present invention toprovide a method for fumigating a large place such as a culturalfacility with a compact apparatus and such an apparatus using the samemethod.

DISCLOSURE OF THE INVENTION

In accordance with a first aspect of the present invention to achievethe aforesaid objects, there is provided a method for fumigation whichcomprises providing an inert gas supply source and a pressure containerfilled with liquid propylene oxide, introducing an inert gas fed fromthe inert gas supply source and liquid propylene oxide fed from thepressure container in advance to a gas-liquid mixer for mixture,introducing the resultant gas-liquid mixture from the gas-liquid mixerto a vaporizer for vaporization, and then introducing the resultant gasmixture to a place to be fumigated.

In accordance with a second aspect of the present invention to achievethe aforesaid objects, there is provided an apparatus for fumigationwhich comprises an inert gas supply source, a pressure container filledwith liquid propylene oxide, a gas-liquid mixer for mixing in advance aninert gas fed from the inert gas supply source and liquid propyleneoxide fed from the pressure container, a vaporizer for vaporizing theresultant gas-liquid mixture introduced from the gas-liquid mixer, andan inlet tube for introducing the resultant gas mixture vaporized by thevaporizer to a place to be fumigated.

According to the present invention, a method for fumigation whichcomprises providing an inert gas supply source and a pressure containerfilled with liquid propylene oxide, introducing an inert gas fed fromthe inert gas supply source and liquid PO fed from the pressurecontainer in advance to a gas-liquid mixer for mixture, introducing theresultant gas-liquid mixture from the gas-liquid mixer to a vaporizerfor vaporization, and then introducing the resultant gas mixture to aplace to be fumigated. In this manner, a fumigating method according tothe present invention uses a gas-liquid mixer and a vaporizer. First,the inert gas fed from the inert, gas supply source and the liquid POfed from the pressure container are mixed in advance by means of agas-liquid mixer, and the resultant gas-liquid mixture is vaporized bymeans of a vaporizer, and then the gas mixture is introduced into theplace to be fumigated. Therefore, in the case of using the vaporizeraccording to the present invention, the installation becomes compact bydownsizing the vaporizer, compared with the conventional bubbling methodwhere the PO tank 58 is put into warm water 62 a of the warm water bath62. Further, compared with the conventional bubbling method where the POtank 58 is heated by warm water 62 a of the warm water bath 62, theamount of heat transmission is larger and the vaporizing speed is fasterin the case of using the vaporizer, so that the dispensing time can beshortened and the dispensing amount can be increased. Therefore, a largeplace such as a cultural facility can be fumigated by the presentmethod. Further, the fumigating method having the aforesaid beneficialeffects can be effectively conducted by using the present apparatus.

When a remaining amount of the liquid PO is indicated by constantlymeasuring the pressure container filled with the liquid propylene oxideby a measuring means in the inventive method or in the inventiveapparatus, the amount supplied and the remaining amount of the liquid POin the pressure container can be found at once by measuring each weightof the pressure container before and after dosage, compared with theconventional bubbling method where the PO tank 58 is put into warm water62 a of the warm water bath 62, which means that the PO tank is fixedwithin the warm water bath during the dispensing process so that it isdifficult to know the amount supplied and the remaining amount of theliquid PO in the conventional bubbling method.

When at least one part of a tube for transporting the gas-liquid mixtureis installed in warm water heated by a heater in a warm water bath ofthe vaporizer so as to vaporize the gas-liquid mixture by warming withthe warm water in the inventive method or in the inventive apparatus, awarm water amount of the warm water bath in the vaporizer could beincreased, so that calorie is increased compared with the conventionalbubbling method where the PO tank 58 is put into the warm water bath 62.For this reason, the vaporizing speed is faster in the inventive methodor the inventive apparatus, time required for dosage could be shortenedand the dosage amount could be drastically increased.

When the gas mixture is diluted by diluting means in the place to befumigated according to the inventive method or the inventive apparatus,the PO gas concentration in the gas mixture could be diluted to thespecific concentration by the diluting means arranged within the placeto be fumigated.

When the propylene oxide gas is contained at a high concentration of 37to 99% by volume in the gas mixture obtained by the vaporizer so as tobe outside a combustible range of the propylene oxide gas while thepropylene oxide gas introduced at the high concentration into thediluting means is diluted to a low concentration of 0.5 to 2.5% byvolume in the gas mixture so as to be again outside a combustible rangeof the propylene oxide gas in the inventive method or in the inventiveapparatus, the PO gas concentration is outside of the combustible rangeduring vaporization in the vaporizer and through an inlet tube forintroducing the PO gas from the vaporizer to the diluting means, whichmeans safety. In the present invention, the PO gas concentration of thegas mixture (diluted gas) diluted by the diluting means is outside thecombustible range, which is safe to be supplied to the place to befumigated. Still further, when the PO gas concentration in the gasmixture is within a combustible range, the gas mixture exists within thediluting means. Therefore, if taking some measures so as not to takefire in the diluting means, safety could be secured within the dilutingmeans. In the present invention, the PO gas concentration is within ahigh range of 37 to 99% by volume in the gas mixture in the presentinvention, more preferably within a range of 55 to 65% by volume. Whenthe PO gas concentration is within a range of 55 to 65% by volume, it isvery safe because the combustible range of the gas mixture is narrow (ortime required to pass the combustible range is shortened). When the POgas concentration is below 55 % by volume or over 65% by volume, thecombustible range is wide, it is rather inferior in safety. When thecombustible range is the narrowest (or time required to pass thecombustible range is the shortest), the PO gas concentration is 60% byvolume, which is the safest.

When the inert gas is an argon gas in the inventive method or theinventive apparatus, there is the advantage that the argon gas may notdamage dye, pigment or the like used for cultural assets, etc.,differently from nitrogen or the like, because the argon gas is acomplete inert gas. Further, since the argon gas has slightly aninsecticidal action by itself, excellent insecticidal action andantiseptic effect can be obtained by combining the argon gas with the POgas. Since the specific gravity of the argon gas is heavier than theair, the argon gas is mixed with the PO gas, lighter than the air, at aspecific rate so that the resulting gas mixture becomes heavier than theair and prevails to the four corners of the place to be fumigated. Theinert gas is not limited to the argon gas and various inert gases suchas nitrogen gas may be used instead of the argon gas in the presentinvention. The inert gas in the present invention includes carbondioxide gas and Freon HFC134a.

When including a gas-mixture inlet tube connected with the inlet tube, afan, both provided within a case of the diluting means, a gas outletformed on the gas-mixture inlet tube, a gas inlet provided within thecase of the diluting means for introducing gas outside the dilutingmeans into the diluting means with rotation of the fan for diluting thegas mixture which flows out of the gas outlet of the gas-mixture inlettube; and a gas outlet, provided within the case of the diluting means,through which the diluted gas flows out, according to the inventivemethod or the inventive apparatus, the gas-mixture introduced into thecase of diluting means through the inlet tube, the gas-mixture inlettube and the gas outlet could be diluted by the gas outside the dilutingmeans (that is, gas existing in the place to be fumigated). For thisreason, the amount of the argon gas used could be greatly reducedcompared with the conventional bubbling method where a large amount ofthe argon gas is used for diluting the PO gas. Further, when introducingthe gas-mixture into an enclosed place 57 to be fumigated more thannecessary, pressure is increased within the place, as in theconventional bubbling method, so that the gas may tend to leak in thecase where sealing degree is low like in general cultural facilities. Onthe other hand, gas leak of the gas-mixture from the place to befumigated could be reduced according to the inventive method or in theinventive apparatus because the amount of the argon gas used is reduced.

When the gas-liquid mixer is provided with a cylinder, an inert-gasinlet for introducing inert gas supplied from an inert-gas supply sourceis provided on a peripheral wall of the cylinder, a liquid-inlet tubefor introducing liquid PO supplied from the pressure container into thecylinder penetrates the peripheral wall of the cylinder so as to passinto an inside of the cylinder and is aligned along a longitudinaldirection of the inside, whereby the liquid PO which flows out of theliquid-inlet tube is mixed with the inert gas which flows out of theinert-gas inlet so that the gas and the liquid are mixed and made into agas-liquid mixture in a mist state, the gas-liquid mixture in a miststate could be obtained by a simple apparatus.

When a lower liquid phase portion comprising liquid PO and an upper gasphase portion in an upper space of the liquid phase portion are providedwithin the pressure container, wherein the inert gas is supplied fromthe inert-gas supply source to the upper gas phase portion, the liquidPO could be pushed out by means of the pressure of the inert gas of theinert-gas supply source.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of one embodiment illustrating a fumigatingapparatus according to the present invention;

FIG. 2 is a cross sectional view partially illustrating a gas-liquidmixer of FIG. 1;

FIG. 3 is a cross sectional view illustrating a diluting means;

FIG. 4 is a block diagram illustrating a modification of a pressureadjusting means; and

FIG. 5 is a block diagram illustrating a conventional apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will next be described in detail.

FIG. 1 illustrates one embodiment of a fumigating apparatus according tothe present invention. In FIG. 1, a reference numeral 1 denotes an argongas tank (an inert gas supply source) in which argon gas is filled in apressurized state. A reference numeral 2 denotes a first decompressionvalve installed in an argon gas takeout tube 3 and the firstdecompression valve 2 depressurizes the pressure (14.7 MPa in thisembodiment) of the argon gas taken out of the argon gas tank 1 to aspecific pressure (0.3 MPa in this embodiment). A reference numeral 4 isan argon gas inlet tube for introducing the argon gas taken out of theargon gas takeout tube 3 into a gas-liquid mixer 5 and an on/off valve 6is aligned upstream of the argon gas inlet tube while an argon gasflowmeter 7 (having an on/off valve 7 a) for adjusting an argon gas flowto a constant rate (240 L/min in this embodiment) is aligned downstreamof the argon gas inlet tube.

A reference numeral 8 is a PO tank (pressure container) in which liquidPO is filled and a space inside the P0 tank is separated into two partsof a lower liquid phase portion 8 a comprising liquid PO and an uppergas phase portion 8 b in an upper space of the lower liquid phaseportion. Reference numerals 9, 10 denote a first and a secondpressurizing argon gas inlet tubes, respectively, for introducing theargon gas taken out of the argon gas takeout tube 3 into the PO tank 8,wherein an on/off valve 11 is aligned upstream and a seconddecompression valve 12 is aligned downstream of the first pressurizingargon gas inlet tube 9, respectively. The second decompression valve 12depressurizes the argon gas pressurized by the first decompression valve2 further to a specific pressure (0.2 MPa in this embodiment). Thesecond pressurizing argon gas inlet tube 10 is provided with an on/offvalve 13 and extends to the upper gas phase portion 8 b of the PO tank8. The inner pressure (the pressure of the upper gas phase portion 8 b)of the PO tank 8 is kept at the same pressure as the specific pressuredepressurized by the second decompression valve 12.

A reference numeral 14 denotes an electronic measuring means providedwith a board 14 a on which the PO tank 8 is placed for measuring theweight of the PO tank and an indicator 14 b for indicating the resultingweight. When the amount supplied and the remaining amount of the liquidPO before/after dosage are needed, the weight of the liquid PO filled inthe PO tank 8 (the amount supplied or the remaining amount) could beobtained by calculating the weight of the PO tank 8 placed on the board14 a.

Reference numerals 16, 17 denote a first liquid inlet tube and a secondliquid inlet tube, respectively for introducing the liquid PO of thelower liquid phase portion 8 a of the PO tank 8 into the gas-liquidmixer 5 and the first liquid inlet tube 16, having an on/off valve 18,extends from a bottom of the PO tank 8. The second liquid inlet tube 17is provided with flowmeter 19 (having an on/off valve 19 a) foradjusting the liquid PO flow to a constant rate (1 L/min in thisembodiment)

As shown in FIG. 2, the gas-liquid mixer 5 comprises a first cylinder 21and a second cylinder 22 screwed on threaded portion 21a formed on anopen end (a left open in FIG. 2) of the first cylinder 21, and the otherend open (not shown) of the first cylinder 21 is connected with a misttransporting means 23 (see FIG. 1). An argon gas inlet 22 a is formed ona peripheral wall of the second cylinder 22 and is provided with an openend of 4 a of the argon gas inlet tube 4. An end portion 17 a of thesecond liquid inlet tube 17 penetrates a left end wall 22 b of thesecond cylinder 22 so as to enter the second cylinder 22 andextend-longitudinally inside the second cylinder. The end portion 17 aof the second liquid inlet tube 17 is opened upstream of the argon gasinlet 22 a. The argon gas which flows out of the argon gas inlet 22 aflows upstream along the end portion 17 a within the second cylinder 22(as shown by arrows in FIG. 2) and is mixed with the liquid PO whichflows out of the end portion 17 a. At that time, the argon gas hasmomentum stronger than the liquid PO due to the difference betweenpressures decompressed by the both decompression valves 2 and 12,whereby the liquid PO is made into a mist state by the argon gas and thegas-liquid mixture in a mist state is led out of the mist transportingmeans 23. In FIG. 2, a reference numeral 22 c is a threaded portion ofthe second cylinder 22 corresponding to the threaded portion 21 a of thefirst cylinder 21.

A reference numeral 25 is a vaporizer adopting an indirect warmingmethod by means of warm water and for vaporizing the gas-liquid mixturein a state of mist led out of the mist transporting tube 23. Thevaporizer 25 comprises a warm water bath 26 for storing warm water 26 a,an electrical heater 27 for heating the warm water 26 a, a tube (tubebody) 28 for vaporization immersed in warm water 26 a of the water bath26, and a temperature controller 29, wherein the temperature of the warmwater 26 a is adjusted to about 80° C. by means of the electrical heater27. Since there is no necessity to control the PO concentration as inthe conventional bubbling method, the temperature in the presentinvention could be higher than that of the conventional bubbling method.An open end of the tube 28 for vaporization is connected with the misttransporting tube 23, and the other end open thereof is connected with agas mixture inlet tube 30 connected with a diluting means 32, belowmentioned. The gas-liquid mixture in a mist state obtained by thegas-liquid mixer 5 is introduced into the tube 28 for vaporizationthrough the mist transporting tube 23, wherein the gas-liquid mixture ina mist state is warmed by the warm water 26 a during passage through thetube 28 for vaporization so as to be vaporized completely, and then besupplied to the gas mixture inlet tube 30.

A reference numeral 32 is a diluting means installed in a place (space)31 to be fumigated. The diluting means 32 dilutes the gas mixtureintroduced through the gas mixture inlet tube 30. As shown in FIG. 3,the diluting means 32 includes a cylinder case 33, an annular tube(gas-mixture inlet tube) 34 provided within the cylinder case 33, and ablower fan 35 (air amount 70 m³/min) provided below the annular tube 34within the cylinder case 33 wherein the annular tube 34 is connectedwith the gas mixture inlet tube 30. Plural inlets 33 a (only two inletsshown in FIG. 3) are made on a peripherally lower part of the cylindercase 33, and an upper open (gas outlet) 33 b is covered by a roof 36supported by a number of bars 36 a (only two bars shown in FIG. 3). Anumber of gas outlets 34 a are formed on the annular tube 34. In FIG. 3,a reference numeral 37 is a bottom plate for sealing the cylinder case33 from beneath and a reference numeral 38 denotes a cylinder guide forguiding gas taken through gas inlets 33 a into a near side to the blowerfan 35. The gas is taken from outside cylinder case 33 into the cylindercase 33 via the gas inlets 33 a, and is moved upward with rotation ofthe blower fan 35, and the gas mixture which flows out of the gas outlet34 a of the annular tube 34 is diluted with the gas taken into thecylinder case 33, and then the diluted gas flows out of the upper open33 b so as to encounter the roof 36 and be sent out to the place 31 tobe fumigated.

A reference numeral 40 denotes a pressure adjusting means formaintaining pressure of the place 31 to be fumigated at a specificpressure (normal pressure in this embodiment). The pressure adjustingmeans 40 includes an air bag 41 expanded by air filled therein, anexhaust fan 42 (an exhaust velocity of 1 m³/min) for exhausting airwithin the air bag 41 to the outside of the place 31 to be fumigated,and a micromanometer 43 for controlling operation of the exhaust fan 42according to the detected pressure of the place 31. When the pressure ofthe place 31 increases along with introduction of the gas mixture, theair is gradually released from the air bag 41 with operation of theexhaust fan 42 so that the pressure in the place may not be increased tothe pressure over the specific pressure. For this reason, thesubstantial volume of the place 31 to be fumigated is reduced and thepressure in the place is lowered so as to be adjusted within thespecific pressure. When the pressure in the place 31 becomes thespecific pressure, the micromanometer 43 detects the pressure so as tostop the operation of the exhaust fan 42 and also stop air release fromthe air bag 41. In FIG. 1, a reference numeral 44 denotes a connectingtube provided with an on/off valve 45. The connecting tube 44 suppliesthe argon gas of the argon tank 1 to the second liquid inlet tube 17,the gas-liquid mixer 5, the mist transporting tube 23, the tube 28 forvaporization of the vaporizer 25 and the inlet tube 30 for cleaning ofthem after a fumigating treatment. The connecting tube 44 connects thefirst pressurizing argon gas inlet tube 9 and the second liquid inlettube 17.

A fumigating process can be conducted using the above apparatus, forexample, as follows. The on/off valves 6, 7 a are opened so that theargon gas of the argon gas tank 1 is introduced into the gas-liquidmixer 5 through the argon gas takeout tube 3 and the argon gas inlettube 4. At that time, the flow rate of the argon gas is adjusted to aconstant rate by means of the argon gas flowmeter 7 in the argon gasinlet tube 4. The on/off valves 11, 13 and 18 are opened and the on/offvalve 45 is closed so that the argon gas of the argon gas tank 1 isintroduced into the upper gas phase portion 8 b of the PO tank 8 throughthe argon gas takeout tube 3 and both of the pressurizing argon gasinlet tubes 9, 10, whereby the liquid PO in the lower liquid phaseportion 8 a of the PO tank 8 is introduced into the liquid PO flowmeter19 through the first liquid inlet tube 16. Then, the on/off valve 19 ais opened so that the liquid PO is introduced into the gas-liquid mixer5 with adjusting the flow rate to a constant rate by the liquid POflowmeter 19. In the gas-liquid mixer 5, the argon gas and the liquid POare made into a gas-liquid mixture in a mist state and led out of themist transporting tube 23. The gas-liquid mixture in a mist state isintroduced into the tube 28 for vaporization of the vaporizer 25 so asto be vaporized completely during passage through the tube 28 forvaporization by the warm water 26 a. In this embodiment, the PO gasconcentration of the gas mixture obtained by vaporization by means ofthe vaporizer 25 is adjusted to 60% by volume and the argon gasconcentration is adjusted to 40% by volume. Further, the flow rate ofthe gas mixture is adjusted to 584 L/min. The gas mixture is led out tothe diluting means 32 through the gas mixture inlet tube 30. The gasmixture in the diluting means 32 is diluted to the degree that the POgas concentration is 0.5 to 2.5% by volume and sent to the outside ofthe diluting means 32. In this manner, a fumigating process is conductedfor a specific time in the place 31 to be fumigated for killing theharmful organisms within the place 31 and then the fumigating process iscompleted. In this embodiment, the ratio of the PO gas and the argon gasis 6:4, whereby the amount for use of the argon gas is drasticallyreduced compared with the conventional bubbling method (PO gas:argongas=2.5:97.5).

Since the gas-liquid mixer 5 and the vaporizer 25 are used for obtainingthe gas mixture of the PO gas and the argon gas in this embodiment, asmentioned above, the installation can be compact. Further, the amount ofheat transmission of vaporization heat is large and the vaporizing speedis fast in the vaporizer 25, so that the dispensing amount can beincreased. Therefore, a large place such as a cultural facility can befumigated by the present method. Still further, since the PO gasconcentration of the gas mixture obtained by means of the vaporizer 25is adjusted to a high concentration of 60% by volume and the PO gas ofthe gas mixture is diluted to a low concentration of 0.5 to 2.5% byvolume in the diluting means 32, each of the PO gas concentrations ofthe gas mixture is outside of the combustible range during vaporizationin the vaporizer 25 and in the inlet tube 30, which means safetytherein. Also it is safe in the diluting means 32. Even still further,the gas-liquid mixer 5 has a simple structure. Further, since the liquidPO of the PO tank 8 is introduced into the gas-liquid mixer 5 by meansof the argon gas in the argon tank 1, the installation can besimplified.

FIG. 4 illustrates a modification of a pressure adjusting means for usein the fumigating apparatus according to the present invention. In thisembodiment, the pressure adjusting means is for maintaining the pressureof the place 31 to be fumigated at a specific pressure (normal pressurein this embodiment) by exhausting the gas of the place 31 to theoutside. The pressure adjusting means includes an on/off valve 47, afilter 48, an exhaust fan 49 and a micromanometer (not shown) forcontrolling operation of the on/off valve 47 and the exhaust fan 49 bydetecting the pressure of the place 31. When the pressure of the place31 increases along with introduction of the gas mixture in thisembodiment, the on/off valve 47 is opened so as not to increase thepressure beyond the specific pressure and the air is gradually releasedto the outside from the place 31 with operation of the exhaust fan 49 sothat the pressure in the place 31 is adjusted to the specific pressure.When the pressure in the place 31 becomes the specific pressure, themicromanometer detects the pressure so as to close the on/off valve 47and stop the operation of the exhaust fan 49 and also stop air releasefrom the place 31.

In the above embodiment, the argon gas tank 1 in which argon gas isfilled at high pressure is used as an argon gas supply source, which,however, is not limited thereto. A liquefied gas container (LGC) filledwith liquid argon may be used by being connected with a vaporizer forvaporizing the liquid argon for use.

The argon gas of the argon gas tank 1 is introduced into the upper gasphase portion 8 b of the PO tank 8 in the above embodiment. However, anycontainers other than the argon gas tank 1 may be used for introducingthe argon gas into the upper gas phase portion 8 b of the PO tank 8, orany gas other than argon gas may be used. Further, any other means maybe used only if it is possible to send out the liquid PO of the lowerliquid phase portion 8 a of the liquid PO tank 8 into the first liquidinlet tube 16.

A gas-exhausting process after the fumigating process may be conductedby combining the conventional vacuum cleaning method (VCM) or acatalytic exhaust gas treatment equipment (VOC-ABATER: Volatile OrganicChemicals Abater) with the fumigating apparatus as shown in FIG. 1.

INDUSTRIAL APPLICABILITY

In the case of using the vaporizer according to the present invention,the installation becomes compact by downsizing the vaporizer, comparedwith the conventional bubbling method where the PO tank 58 is put intowarm water 62 a of the warm water bath 62. Further, compared with theconventional bubbling method where the PO tank 58 is heated by warmwater 62 a of the warm water bath 62, the amount of heat transmission islarger and the vaporizing speed is faster in the case of using thevaporizer, so that the dispensing time can be shortened and thedispensing amount can be increased. Therefore, a large place such as acultural facility can be fumigated by the present method. Further, thefumigating method having the aforesaid beneficial effects can beeffectively conducted by using the present apparatus.

When a remaining amount of the liquid PO is indicated by constantlymeasuring the pressure container filled with the liquid propylene oxideby a measuring means in the inventive method or in the inventiveapparatus, the amount supplied and the remaining amount of the liquid POin the pressure container can be found by measuring each weight of thepressure container before and after dosage, compared with theconventional bubbling method where the PO tank 58 is put into warm water62 a of the warm water bath 62, which means that the PO tank is fixedwithin the warm water bath during the dispensing process, so that it isdifficult to know the amount supplied and the remaining amount of theliquid PO in the conventional bubbling method.

When at least one part of a tube for transporting the gas-liquid mixtureis installed in warm water heated by a heater in a warm water bath ofthe vaporizer so as to vaporize the gas-liquid mixture by warming withthe warm water in the inventive method or in the inventive apparatus, awarm water amount of the warm water bath in the vaporizer could beincreased, so that calorie is increased compared with the conventionalbubbling method where the PO tank 58 is put into the warm water bath 62.For this reason, the vaporizing speed is faster in the inventive methodor the inventive apparatus, time required for dosage could be shortenedand the dosage amount could be drastically increased.

When the gas mixture introduced is diluted by diluting means in theplace to be fumigated according to the inventive method or the inventiveapparatus, the PO gas concentration in the gas mixture could be dilutedto the, specific concentration by the diluting means arranged within theplace to be fumigated.

When the propylene oxide gas is contained at a high concentration of 37to 99% by volume in the gas mixture obtained by the vaporizer so as tobe outside a combustible range of the propylene oxide gas while thepropylene oxide gas introduced at the high concentration into thediluting means is diluted to a low concentration of 0.5 to 2.5% byvolume in the gas mixture so as to be again outside a combustible rangeof the propylene oxide gas in the inventive method or in the inventiveapparatus, the PO gas concentration is outside of the combustible rangeduring vaporization in the vaporizer and through an inlet tube forintroducing the PO gas from the vaporizer to the diluting means, whichmeans safety. In the present invention, the PO gas concentration of thegas mixture (diluted gas) diluted by the diluting means is outside thecombustible range, which is safe to be supplied to the place to befumigated. Still further, when the PO gas concentration in the gasmixture is within a combustible range, the gas mixture exists within thediluting means. Therefore, if taking some measures so as not to takefire in the diluting means, safety could be secured within the dilutingmeans. In the present invention, the PO gas concentration is within ahigh range of 37 to 99% by volume in the gas mixture in the presentinvention, more preferably within a range of 55 to 65% by volume. Whenthe PO gas concentration is within a range of 55 to 65% by volume, it isvery safe because the combustible range of the gas mixture is narrow (ortime required to pass the combustible range is shortened). When the POgas concentration is below 55% by volume or over 65% by volume, thecombustible range is wide, it is rather inferior in safety. When thecombustible range is the narrowest (or time required to pass thecombustible range is the shortest), the PO gas concentration is 60% byvolume, which is the safest.

When the inert gas is an argon gas in the inventive method or theinventive apparatus, there is the advantage that the argon gas may notdamage dye, pigment or the like used for cultural assets, etc.,differently from nitrogen or the like, because the argon gas is acomplete inert gas. Further, since the argon gas has slightly aninsecticidal action by itself, excellent insecticidal action andantiseptic effect can be obtained by combining the argon gas with the POgas. Since the specific gravity of the argon gas is heavier than theair, the argon gas is mixed with the PO gas, lighter than the air, at aspecific rate so that the resulting gas mixture becomes heavier than theair and prevails to the four corners of the place to be fumigated.

When including a gas-mixture inlet tube connected with the inlet tube, afan, both provided within a case of the diluting means, a gas outletformed on the gas-mixture inlet tube, a gas inlet provided within thecase of the diluting means for introducing gas outside the dilutingmeans into the diluting means with rotation of the fan for diluting thegas mixture which flows out of the gas outlet of the gas-mixture inlettube with the gas introduced; and a gas outlet, provided within the caseof the diluting means, through which the diluted gas flows out,according to the inventive method or the inventive apparatus, thegas-mixture introduced through the inlet tube, the gas-mixture inlettube and the gas outlet could be diluted by the gas outside the dilutingmeans (that is, gas existing in the place to be fumigated). For thisreason, the amount of the argon gas used could be greatly reducedcompared with the conventional bubbling method where a large amount ofthe argon gas is used for dilution. Further, when introducing thegas-mixture into an enclosed place 57 to be fumigated more thannecessary, pressure is increased within the place 57, as in theconventional bubbling method, so that the gas may tend to leak in thecase where sealing degree is low like in general cultural facilities. Onthe other hand, gas leak of the gas-mixture from the place to befumigated could be reduced according to the inventive method or in theinventive apparatus because the amount of the argon gas used is reduced.

When the gas-liquid mixer is provided with a cylinder, an inert-gasinlet for introducing inert gas supplied from an inert-gas supply sourceis provided on a peripheral wall of the cylinder, a liquid-inlet tubefor introducing liquid PO supplied from the pressure container into thecylinder penetrates the peripheral wall of the cylinder so as to passinto an inside of the cylinder and is aligned along a longitudinaldirection of the inside, whereby the liquid PO which flows out of theliquid-inlet tube is mixed with the inert gas which flows out of theinert-gas inlet so that the gas and the liquid are mixed and made into agas-liquid mixture in a mist state, the gas-liquid mixture in a miststate could be obtained by a simple apparatus.

When a lower liquid phase portion comprising liquid PO and an upper gasphase portion in an upper space of the liquid phase portion are providedwithin the pressure container, wherein the inert gas is supplied fromthe inert-gas supply source to the upper gas phase portion, the liquidPO could be pushed out to the outside of the pressure container by meansof the pressure of the inert gas of the inert-gas supply source.

1. A method for fumigation which comprises providing an inert gas supplysource and a pressure container filled with liquid propylene oxide,introducing an inert gas fed from the inert gas supply source and liquidpropylene oxide fed from the pressure container in advance to agas-liquid mixer for mixture, introducing the resultant gas-liquidmixture from the gas-liquid mixer to a vaporizer for vaporization, andthen introducing the resultant gas mixture to a place to be fumigated.2. A method as set forth in claim 1, wherein a remaining amount of theliquid propylene oxide is indicated by constantly measuring the pressurecontainer filled with the liquid propylene oxide by a measuring means.3. A method as set forth in claim 1, wherein at least one part of a tubefor transporting the gas-liquid mixture is installed in warm waterheated by a heater in a warm water bath of the vaporizer so as tovaporize the gas-liquid mixture by warming with the warm water.
 4. Amethod as set forth in claim 1, wherein the gas mixture is diluted bydiluting means in the place to be fumigated.
 5. A method as set forth inclaim 4, wherein the propylene oxide gas is contained at a highconcentration of 37 to 99% by volume in the gas mixture obtained by thevaporizer so as to be outside a combustible range of the propylene oxidegas while the propylene oxide gas introduced at the high concentrationinto the diluting means is diluted to a low concentration of 0.5 to 2.5%by volume in the gas mixture so as to be again outside a combustiblerange of the propylene oxide gas.
 6. A method as set forth in claim 1,wherein the inert gas is an argon gas.
 7. An apparatus for fumigationwhich comprises an inert gas supply source, a pressure container filledwith liquid propylene oxide, a gas-liquid mixer for mixing in advance aninert gas fed from the inert gas supply source and liquid propyleneoxide fed from the pressure container, a vaporizer for vaporizing theresultant gas-liquid mixture introduced from the gas-liquid mixer, andan inlet tube for introducing the resultant gas mixture vaporized by thevaporizer to a place to be fumigated.
 8. An apparatus as set forth inclaim 7, wherein a measuring means is provided for constantly measuringthe pressure container filled with the liquid propylene oxide so as toobtain a remaining amount of the liquid propylene oxide.
 9. An apparatusas set forth in claim 7, wherein the vaporizer comprises a warm waterbath for storing warm water, a heater for heating the warm water and atube for transporting the gas-liquid mixture, at least one part of thetube being installed in the warm water.
 10. An apparatus as set forth inclaim 7, wherein diluting means is installed for diluting the gasmixture introduced through the inlet tube into the place to befumigated.
 11. An apparatus as set forth in claim 10, wherein thepropylene oxide gas is contained at a high concentration of 37 to 99% byvolume in the gas mixture obtained by the vaporizer while the propyleneoxide gas introduced through the inlet tube into the diluting means isdiluted to a low concentration of 0.5 to 2.5% by volume in the gasmixture.
 12. An apparatus as set forth in claim 10, including agas-mixture inlet tube connected with the inlet tube, a fan, bothprovided within a case of the diluting means, a gas outlet formed on thegas-mixture inlet tube, a gas inlet provided within the case of thediluting means for introducing gas outside the diluting means into thediluting means with rotation of the fan for diluting the gas mixturewhich flows out of the gas outlet of the gas-mixture inlet tube with thegas introduced; and a gas outlet, provided within the case of thediluting means, through which the diluted gas flows out.
 13. Anapparatus as set forth in claim 7, wherein the gas-liquid mixer isprovided with a cylinder, an inert-gas inlet for introducing inert gassupplied from an inert-gas supply source is provided on a peripheralwall of the cylinder, a liquid-inlet tube for introducing liquidpropylene oxide supplied from the pressure container into the cylinderpenetrates the peripheral wall of the cylinder so as to pass into aninside of the cylinder and is aligned along a longitudinal direction ofthe inside, whereby the liquid propylene oxide flowing out of theliquid-inlet tube is mixed with the inert gas flowing out of theliquid-inlet tube so that the gas and the liquid are mixed and made intoa gas-liquid mixture in a mist state.
 14. An apparatus as set forth inclaim 7, wherein a lower liquid phase portion comprising liquidpropylene oxide and an upper gas phase portion in an upper space of theliquid phase portion are provided within the pressure container, and theinert gas is supplied from the inert-gas supply source to the upper gasphase portion.
 15. An apparatus as set forth in claim 7, wherein theinert gas is an argon gas.